Introduction and Objective: Microarray technology and proteomic approaches promise to become a pivotal tool in understanding the functional genomics of complex diseases. Critically ill or injured patients frequently die of incompletely understood conditions such as septic shock, acute respiratory distress syndrome, and ultimately multiple organ dysfunction syndrome. Host inflammatory pathways are thought to play major pathogenic roles in these syndromes. At a basic level, the clinical and biological manifestations of host responses are determined or at least reflected by quantitative and qualitative changes in gene expression. Therefore, organ injury syndromes might be defined by their associated patterns of altered gene expression. Oligonucleotide microarrays can measure relative changes in mRNA levels for thousands of genes simultaneously providing a global snapshot of the transcriptome. The goals of this line of investigation include: 1) to link pathophysiology and/or interventions with responding genes; 2) identify system characteristics, signaling pathways, and regulatory networks important to critical illness; 3) discover biomarkers, prognostic indicators, and potential targets for drug development. Progress: Development of laboratory procedures for handling a variety of sample types including neutrophils, peripheral blood mononuclear cells, T-lymphocytes, whole blood broncheoalveolar lavage, spleen, liver, lung, and heart. Standard approaches to amplication of small samples tested. Experience obtained with oligonucleotide microarrays for several species including human, mouse and rat. Construction and extensive testing of a data analysis pipeline. Establishment of a database and web based analytical tools. Investigation of interactions between interferon g and dexamethasone in primary bronchial epithelial cells. Identification of the expression profiles associated with sickle cell anemia, endotoxin challenge in normal volunteers, and escalating severity of infection in a rat model. Proposed Course of Work: Define the in vitro response of primary human cells including neutrophils, monocytes, and endothelial cells to endotoxin and other immune activators. Determine whether infection with different types of bacteria produce organism-specific signatures in a rat model of pneumonia. Using knockout mice with specific genetic defects serially examine the severity of sepsis-induced myocardial dysfunction, associated changes in gene expression, and outcome. Identify biomarkers of disease severity and outcome in sickle cell anemia.